1. Field of the Invention
The present invention relates to a switchgear in which an electrode opening or closing operation is performed when the electrode contacts or separates, particularly to a switchgear having a simplified structure and improved performance.
2. Description of the Related Art
FIGS. 25A and 25B show a switchgear similar to a conventional switchgear using electromagnetic repulsion as shown in Japanese Patent Publication No. 7-60624. Further, FIG. 25A shows the closed electrode state and FIG. 25B shows the opened electrode state.
In the figures, a switch 1 has a movable electrode 5 and a fixed electrode 6. The movable electrode 5 is fixed to a movable conductive rod 4. A repulsing section 2 is fixed to the movable conductive rod 4. A coil 3 for inducing-current in the repulsing section 2 is fixed to a coil holder 9. The repulsing section 2 is pushed by a spring (coil spring) 8 so as to contact the movable electrode 5 with the fixed electrode 6. One end portion of the movable conductive rod 4 is inserted into a latch 7. The repulsing section 2, movable conductive rod 4, and movable electrode 5 are fixed and constituted on the axis of the electrodes 5 and 6. The coil 3 is connected to magnetic-field generating power supply.
Next, FIG. 26 is an illustration showing load characteristics of a coil spring used as the loading spring 8. In FIG. 26, numeral 49 denotes deflection of the spring used, 50 denotes deflection in an electrode closed state, 51 denotes deflection in the opened electrode state, 52 denotes a spring load under the closed electrode state, and 53 denotes a spring load under the opened electrode state.
Next, the operation will be described. In FIGS. 25A and 25B, when current is supplied to the coil 3, a magnetic field is generated. Thereby, an induced current is generated in the repulsing section 2 to provide an electromagnetic repulsion against the coil 3. When the electromagnetic repulsion exceeds the spring load 52 during the closed electrode state shown in FIG. 26, the repulsing section 2, movable conductive rod 4, and movable electrode 5 operate in the same direction as the electromagnetic repulsion and the switch 1 opens. Then, the latch 7 keeps the positions of the repulsing section 2, movable conductive rod 4, and movable electrode 5 in an opened electrode state, the switch 1 can then be closed in accordance with the load of the loading spring 8 by releasing the latch 7. As shown in FIG. 26, because the spring constant of the coil spring is constant, the spring load 53 in the opened electrode state exceeds the load 52 under the closed electrode state.
As described above, because the conventional switchgear uses the coil spring as the loading spring 8 and the spring load under the opened electrode state is larger than that under the closed electrode state, the spring energy must be large while the closed electrode state changes to the opened electrode state, therefore requiring unnecessary electromagnetic repulsion energy. Moreover, conventional switchgear needs a latch mechanism to maintain the opened electrode state. Therefore, when the electrode opening speed increases, the latch performance can not keep up with the speed and thus, the opened electrode state cannot be maintained. Furthermore, because the closing operation is performed by releasing the latch 7, there are problems in that it takes time for the latch releasing mechanism to begin operation, delaying the closing operation.